import sys
from time import sleep
import pygame

from alien import Alien
from bullet import Bullet

# =============================
# 一、事件处理
# =============================

def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """响应按键按下事件"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        if len(bullets) < ai_settings.bullets_allowed:
            new_bullet = Bullet(ai_settings, screen, ship)
            bullets.add(new_bullet)
    elif event.key == pygame.K_q:
        sys.exit()

def check_keyup_events(event, ship):
    """响应按键松开事件"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False

def check_events(ai_settings,stats,play_button, screen, ship, bullets, aliens):
    """监听键盘和鼠标事件"""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event, ai_settings, screen, ship, bullets)
        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)
        elif event.type == pygame.MOUSEBUTTONDOWN:
            mouse_x, mouse_y = pygame.mouse.get_pos()
            check_play_button(ai_settings, stats,screen,aliens,ship,bullets, play_button, mouse_x, mouse_y)

# =============================
# 二、屏幕更新
# =============================

def update_screen(ai_settings, screen,stats, ship, aliens, bullets, play_button, scoreboard):
    """更新屏幕上的图像，并切换到新屏幕"""
    screen.fill(ai_settings.bg_color)

    for bullet in bullets.sprites():
        bullet.draw_bullet()

    ship.blitme()
    aliens.draw(screen)

    scoreboard.draw_score()

    # 游戏是否是开始状态
    if not stats.game_active:
        play_button.draw_button()

    pygame.display.flip()

# =============================
# 三、子弹处理
# =============================

def update_bullets(ai_settings, screen,stats, ship, aliens, bullets, scoreboard):
    """更新子弹位置，并删除已消失的子弹"""
    bullets.update()

    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)

    check_bullet_alien_collisions(ai_settings, screen, stats, ship, bullets, aliens, scoreboard)

# =============================
# 四、外星人生成与管理
# =============================

def get_number_aliens_x(ai_settings, alien_width):
    """计算每行可以容纳多少个外星人"""
    available_space_x = ai_settings.screen_width - 2 * alien_width
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return number_aliens_x

def get_number_rows(ai_settings, alien_height, ship_height):
    """计算屏幕可容纳多少行外星人"""
    available_space_y = ai_settings.screen_height - (3 * alien_height) - ship_height
    number_rows = int(available_space_y / (2 * alien_height))
    return number_rows

def create_alien(ai_settings, screen, aliens, alien_number, row_number):
    """创建一个外星人并放入当前行的指定位置"""
    alien = Alien(ai_settings, screen)
    alien_width = alien.rect.width
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
    aliens.add(alien)

def create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    alien = Alien(ai_settings, screen)
    number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
    number_rows = get_number_rows(ai_settings, alien.rect.height, ship.rect.height)

    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number, row_number)

# =============================
# 五、外星人移动与碰撞
# =============================

def check_fleet_edges(ai_settings, aliens):
    """检测是否有外星人到达屏幕边缘"""
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break

def change_fleet_direction(ai_settings, aliens):
    """整群外星人下移，并改变方向"""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1

def update_aliens(ai_settings, stats, screen, ship, aliens, bullets):
    """更新所有外星人位置，并检测是否有碰撞"""
    check_fleet_edges(ai_settings, aliens)
    aliens.update()

    # 检查外星人与飞船的碰撞
    if pygame.sprite.spritecollideany(ship, aliens):
        print('Ship hit!!')
        ship_hit(ai_settings, stats, screen, ship, aliens, bullets)

    # 检查是否有外星人到达最底端
    check_alies_bottom(ai_settings, stats, screen, ship, aliens, bullets)

def check_alies_bottom(ai_settings, stats, screen, ship, aliens, bullets):
    """检查是否有外星人到达了屏幕底端"""
    screen_rect = screen.get_rect()
    for alien in aliens:
        if alien.rect.bottom >= screen_rect.bottom:
            # 有没有被消灭的外星人移动到了屏幕外侧
            ship_hit(ai_settings, stats, screen, ship, aliens, bullets)

# =============================
# 六、碰撞检测逻辑
# =============================

def check_bullet_alien_collisions(ai_settings, screen,stats, ship, bullets, aliens, scoreboard):
    """响应子弹和外星人的碰撞"""
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)

    # 击落飞船，累加得分
    if collisions:
        for aliens in collisions.values():
            # 累加得分
            stats.score += ai_settings.alien_points * len(aliens)
            # 重新渲染更新到屏幕上
            scoreboard.prep_score()

    if len(aliens) == 0:
        bullets.empty()
        # 加快难度
        ai_settings.increase_speed()
        create_fleet(ai_settings, screen, ship, aliens)

# =============================
# 七、飞船被撞逻辑
# =============================

def ship_hit(ai_settings, stats, screen, ship, aliens, bullets):
    """响应飞船被外星人撞到"""
    if stats.ships_left > 0:
        # 减少复活次数
        stats.ships_left -= 1
        # 删除飞船和外星人重新开始
        aliens.empty()
        bullets.empty()
        # 重新创建
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()
        # 等待0.5s后开启
        sleep(0.5)
    else:
        # 没有复活机会了 游戏结束
        stats.game_active = False
        # 显示光标
        pygame.mouse.set_visible(True)


    # =============================
# 八、检测按钮事件
# =============================
def check_play_button(ai_settings, stats,screen,aliens,ship,bullets, play_button, mouse_x, mouse_y):
        # 在玩家单击play按钮时 触发开始新游戏
        play_button_click = play_button.rect.collidepoint(mouse_x, mouse_y)
        # 点击按钮位置，且当前游戏是未开始状态
        if play_button_click and not stats.game_active:
            # 隐藏光标
            pygame.mouse.set_visible(False)
            # 重置游戏统计信息
            stats.reset_stats()
            # 重置游戏进度
            ai_settings.initialize_dynamic_settings()

            stats.game_active = True

            # 删除飞船和外星人重新开始
            aliens.empty()
            bullets.empty()
            # 重新创建
            create_fleet(ai_settings, screen, ship, aliens)
            ship.center_ship()